Means for measuring the tension in a strip or sheet shaped material



Se t. 7, 1965 H. FRIMAN ETAL 3,204,454

MEANS FOR MEASURING THE TENSION IN A STRIP OR SHEET SHAPED MATERIAL Filed Feb. 21, 1962 Measuring means INVENTORS How an F: mm! E 4/1. AVA/( ID A TrolA/E/S United States Patent 3,204,454 MEANS vFOR MEASURING THE TENSION IN A STRIP 0R SHEET SHAPED MATERIAL Holger Frima'n and Egil Angeid, Vasteras, Sweden, as-

signors to Allmanna Svenska Elektriska Aktiebolaget, Vasteras, Sweden, :1 Swedish corporation Filed Feb. 21, 1962, Ser. No. 174,903 4 Claims. (Cl. 73-143) When cold rolling strip or sheet material the thickness and surface smoothness of the material will to a great extent be dependent upon the tension with which the material is drawn through the rolling mill when it is rolled onto a reel. The said tension is called the reel strip tension and it should have a definite relation to the rolling speed in order to give an even strip thickness. It is therefore necessary in one way or another to measure the strip tension and use this measured value to control a revolution regulator for either the rolling motor or the reel motor.

When the rolling material comes out of the operating rollers, it is carriedover a bending roller and further to the reel for rolling onto this. When it passes over the bending roller the material is bent an angle a, the size of which varies depending on the amount of rolling material which is already wound onto the reel. The reel strip tension influences the bending roller with'a force which can be divided into a horizontal and a vertical component. These two components depend not only on the strip tension, but also on the angle a, and since the angle varies the two force components will vary continually, both separately and mutually.

Solving the problem of measuring the strip tension has been attempted by placing another roller between the bending roller and the reel. The strip tension then infiuences the bending roller at a constant angle and is thus also easy to measure. The disadvantage with this arrangement, however, is that the distance between the operating rollers and the reel increases which causes a larger amount of material to be scrapped which has not 'been properly rolled. This disadvantage is particularly evident in the rolling method indicated in FIGURE 1 where there is one reel on each side of the rolling mill and the rolling material is driven forwards and backwards without being detached from the reels. A strip of the rolling material corresponding to the distance between the operating rollers and the reel at each end of the material is not rolled and must be scrapped. The aim is therefore to place the reel as near to the operating rollers as possible whilst still being able to continually measure the reel strip tension independent of the amount of rolling material on the reel.

In the accompanying drawings FIGURE 1 shows schematically how the measuring device is placed in a rolling mill. FIGURE la shows how the strip tension S influences the bending roller and the resultant force F together with its vertical and horizontal components, While FIGURE lb shows in larger scale a supporting means with inserted pressure sensing means for the bending roller. FIGURES 2 and 3 show two embodiments of the measuring circuit which is used for generating an electric magnitude which is proportional to the strip tension.

According to FIGURE 1, the rolling material 1 is carried between two operating rollers 2 from one of two reels 3 to the other. Between the operating rollers and each reel a bending roller 4 is arranged which bends the rolling material the angle a. The tension of the rolling material, the reel strip tension, is designated S. According to the figures the reel strip tension brings about a resultant force F on the bending roller, and this force varies both in size and direction when a varies. The

3,204,454 Patented Sept. 7, 1965 angle a varies between two values which correspond to empty and fully rolled reel.

The bending roller 4 is supported by two supporting means 41, each of which contains two pressure sensing means 42 and 43, which transforms two components of the resultant force F to corresponding electrical quantities. These two pressure sensing means are suitably placed so that one of them, 42, senses the horizontal component F and the second one, 43, senses the vertical component F of the resultant force F. From FIGURE la is obtained that:

sin a The pressure sensing means in the bending roller support transforms the force components F and F to voltages U and U proportional thereto. These voltages are supplied to input terminals 5 and 6 respectively in a measuring device according to FIGURE 2. A non-linear potentiometer 7 with movable contact 10 is connected to the terminals 5, while another non-linear potentiometer 8 with movable contact 11 is connected to the terminals 6. One end of each potentiometer is connected to a conductor 12, to which one of each of the terminals 5 and 6 is connected. A servo-means 9 is connected to the two movable contacts 10 and 11. This servo-means senses the voltage difference between the contacts and adjusts them so that the voltage between them is always zero.

From the equation 8: 1cos a and S s= and s= sin or 1-cos or obtained:

Fv FH which lies between the contact 11 and the conductor 12 will be 1-cos on where in both cases k is a constant. If the resistance 7 is taken to be R it is obtained that the current through this is However, since no current flows through the servo-means 9, it is also obtained that the current through R is sin at where U is the voltage difference between the contact 10 and the conductor 12. If these two expressions for the current are equal it is obtained that Sin 0:

3 As previously mentioned U is proportional to F and may be written as U zk -F where k is another constant, but F zS-sin on, from which is obtained U zzk -S'sin on If this is taken in conjunction with the above expression for U is obtained:

and thus the voltage U is proportional to the reel strip tension S independent of the angle The voltage U may be used as an error signal to regulate the reel motor in a known manner, so that the strip tension remains constant. The said voltage may of course also be used to regulate the rolling mill motor or to simultaneously regulate both the rolling mill motor and the reel motor.

Since the angle a normally varies between about 20 and 40 and the curves for sin a and cos on within this interval with reasonable approximation may be replaced by a straight line, the circuit according to FIGURE 2 can be simplified by replacing the non-linear potentiometers by a series connection of a stationary resistance and a linear potentiometer. FIGURE 3 shows such a measuring arrangement. The voltage U influences, via the terminals 5, a series connection of a potentiometer 13 and a stationary resistance 14, while the voltage U influences a series connection of a potentiometer 15 and a stationary resistance 16. The movable contacts 17 and 18 of the two potentiometers are connected to a servom'eans 9 which adjusts them so that the voltage between them is zero. As previously shown, the voltage U between either of the movable contacts 17 or 18 and the conductor 12 will therefore be proportional to the strip tension S and independent of the bending angle a.

A rough measurement of the strip tension can also be obtained through the expression U w U -k U Since the angle a varies within the range 20-40, the greatest fault (with k :1.71) will be about i6%, which in many cases is sufliciently accurate. This solution requires no servo-system.

We claim:

1. Means for measuring the tension in an elongated material which is led over a bending roller to a driven rolling-up reel, the tension of the material exerting on the bending roller, a force dependent upon the tension and the angle at which the material is bent at the bending roller, comprising supporting means for said bending roller containing pressure sensing means for converting two components of said force on said bending roller into two corresponding electrical quantities, a measuring device, means to supply said two electrical quantities to said measuring device, said measuring device including two movable contact potentiometer circuits, each potentiometer circuit receiving one of said electrical quantities, said measuring device having a servo-mechanism responsive to the voltage diiference which prevails between the movable contacts of said potentiometers, said servo-mechanism including means for adjusting said movable contacts until the voltage between them is zero.

2. Means according to claim 1, said potentiometer circuits containing non-linear potentiometers.

3. Means according to claim 1, said potentiometer circuits containing a series connection of a linear potentiometer and a resistance.

4. Means according to claim 1, said measuring device having two output terminals with one of its output terminals connected to the movable contact of one of said potentiometer circuits while the other output terminal is connected to a conductor, both said potentiometer circuits being connected at one end to said conductor.

References Cited by the Examiner FOREIGN PATENTS 3/48 Canada.

RICHARD C. QUEISSER, Primary Examiner.

ROBERT EVANS, Examiner. 

1. MEANS FOR MEASURING THE TENSION IN AN ELONGATED MATERIAL WHICH IS LED OVER A BENDING ROLLER TO A DRIVEN ROLLING-UP REEL, THE TENSION OF THE MATERIAL EXERTING ON THE BENDING ROLLER, A FORCE DEPENDENT UPON THE TENSION AND THE ANGLE AT WHICH THE MATERIAL IS BENT AT THE BENDING ROLLER, COMPRISING SUPPORTING MEANS FOR SAID BENDING ROLLER CONTAINING PRESSURE SENSING MEANS FOR CONVERTING TWO COMPONENTS OF SAID FORCE ON SAID BENDING ROLLER INTO TWO CORRESPONDING ELECTRICAL QUANTITIES, A MEASURING DEVICE, MEANS TO SUPPLY SAID TWO ELECTICAL QUANTITIES TO SAID 